Double-edged knife



FIG. 1 is a perspective view of a double-edged knife, showing my new design;

FIG. 2 is a front elevational view, the rear being a mirror image thereof;

FIG. 3 is a side elevational view, the opposite side being a mirror image thereof;

FIG. 4 is a bottom plan view thereof; and

FIG. 5 is a top plan view thereof. 

The ornamental design for a double-edged knife, as shown and described. 